FIG 1 .

Identification of the CtpA interaction partner PA4667/LbcA. (A) Tandem affinity tag purification. Proteins were purified from detergent-solubilized lysates of the wild-type strain (CtpA) or derivatives encoding CtpA-FLAG-His₆ or the proteolytically inactive CtpA-S302A-FLAG-His₆. Purification was done with nickel agarose (stage 1) followed by anti-FLAG M2 agarose resin (stage 2). Samples were separated on a 12.5% SDS-polyacrylamide gel, which was stained with silver. Molecular mass marker proteins (in kilodaltons) are labeled on the right-hand side. (B) Immunoblot analysis of detergent-solubilized lysate and stage 1 and 2 purified samples, prepared as in panel A. LbcA and CtpA were detected with polyclonal antisera. Strains in which CtpA or CtpA-S302A were not tagged with FLAG-His₆ served as negative controls. Approximate positions of molecular mass marker proteins (in kilodaltons) are indicated on the left-hand side.